Drop in pH Help

Not sure whether I should be concerned about this yet or not, but after my big tank revamp the other day, one of them has dropped its pH from 7.4 to around 6.8 (maybe even 6.6, can't quite tell).

Before creating my two different aquariums I had one tank, moderately planted, a smallish piece of driftwood and a small beach rock (tested positive for calcium, but figured it was only small and the driftwood should offset it's effect on pH, which seemed to be ok), pH was stable at around 7.3. The new tank which is dropping pH has the substrate (gravel), plants and driftwood from the old aquarium, plus three other pieces of wood (all off-cuts from the same larger piece which is now in the other aquarium) but no beach rock. Have I overdone it on driftwood? That's the only real difference I can come up with, other than the temperature is now a bit lower 17c as opposed to 21c).

Just as a reference, I tested both aquariums as well as the water I use for changes (dechlorinated, left standing for a few days) as a control:

Control: 7.4 (tested on high and normal range tests) Temperate tank: >7.4, ever so slightly more orange than the control on the high range. Cold (planted, wooded) tank: 6.6-6.8

They both have the same water, are treated pretty much the same, the only real difference is the extra wood, but I had thought that would take longer than a couple days to affect pH that dramatically?

It would appear to me that the lower pH is a result of the driftwood. I don't know that it is anything to be concerned about, but if you feel you want to raise the pH but still keep the driftwood in the tank, you could add some crushed coral in a media bag and place it in your filter (if it will fit) or just put it directly into the tank. I can't tell you an exact amount, since it's a trial and error process, but I would start with maybe 1/4 cup.

Thanks for the reassurance! I presume driftwood will only drop the pH so far before it levels out? Any ideas just how low that is? I'm not overly concerned about it at the moment, there are two goldfish in this tank who seem perfectly happy... Although perhaps a little sluggish as they adjust to the (gradually lowered) temperature.

I'll continue to monitor it and see how it goes, I may pop one of these beach rocks in after a week and see if it starts to lift it a little.

I think the effect of driftwood depends on your water. For example, I've had tea-colored water in all my tanks due to various pieces of driftwood and the pH never budges from 7.9. My KH is around 6 drops, so I assume that's enough of a buffering capacity to hold the pH steady. My parents have KH around 23 drops (no joke) and I doubt I will ever see a change in pH from 8.8, no matter how dark the water gets from the tannins (and it gets DARK, let me tell you!). So I imagine if you let the tannins accumulate, and if you have water without a lot of buffering capacity, your "bottomed out" value could be pretty low.

If I recall correctly, beach rock and coral should serve as a buffer as well. What gives my parents' water such high KH is that it's well water filtered through many layers of limestone, which is basically coral smashed into rock by weight and time, lol.

Your weekly water changes should keep the Ph from dropping too low I wouldn't add crushed coral to buffer it, a stable Ph is better than a constantly fluctuating one. Just keep monitoring it to make sure it doesn't get too low.

Although there's that big drop in pH, these woods are actually releasing no tannins at all (I did season them fairly well some time ago). The dim lighting and heavy plant cover in this tank make it look very dark on there, but when I pop a brighter light on the water is crystal clear... A shame really, I was hoping for a nice bit if discolouration!

I had my general hardness tested at a LFS some time ago, I forget which scale they were using (I've never taken the time to learn the different ones and how they correlate) but it was 80... 80 'what's', I couldn't tell you, but 80 'something's' anyway.

That's very interesting, I remember at the time she commented that it was quite soft for our area (I've only been here a few years, water hardness hasn't been top of my list of things to do!). I've since spoken to a number of aquarists who have mentioned just how hard the water here generally is.

Can you give me an 'idiots guide' to buffering? Harder water lessens the effect of pH altering substances (ie, driftwood), is that the gist I'm getting here?

That's very interesting, I remember at the time she commented that it was quite soft for our area (I've only been here a few years, water hardness hasn't been top of my list of things to do!). I've since spoken to a number of aquarists who have mentioned just how hard the water here generally is.

Can you give me an 'idiots guide' to buffering? Harder water lessens the effect of pH altering substances (ie, driftwood), is that the gist I'm getting here?

Note that GH does not have to be higher than KH (that is, GH doesn't measure KH + other hardness). As I think I mentioned here, my parents have insanely high KH, but in the same water, the GH test measures 0 because it runs through a water softener and all the minerals that would be caught by a GH test are turned into sodium or potassium or something, which I believe the GH test does not catch. So while KH often comes from water filtering through things that have calcium in them (like limestone), which in turn tends to lead to higher GH (think limescale, etc.), you can actually have water that is 0 GH (per the API test) and 23+ drops KH.

Both are good articles but neither (unless I missed it) mention water changes, unless you ensure the new water is the same as the water in the tank then every time you do a water change the parameters will alter which are not good for your fish. The only reliable way to ensure no swings & keep the ph stable is to use Ro/Di water & remineralise or a 50/50 Ro & tap water, which can be time consuming & costly. Imo it's best not to try & alter your ph & keep fish that are suitable for the water you have.

Took samples to the store today: Temperate (driftwood and beach rock) read a pH of 7.8 and GH of 125.3. Cold (lots of wood, no rock) had pH of 7, GH of107.4.

She tested them both three times, just to be safe. It was a few months ago I last had the GH tested, I'm surprised it's changed that much. I'll have to dig out my notes when I get home and see if my memory isn't just failing me...

After sitting and looking at my aquariums over dinner I've decided I will pull the beach rocks out of the temperate tank and observe the pH over the coming week. I would have thought the size of the new driftwood in there (cut from the same piece as those affecting the cold tank) would have been more than enough to balance them out, but obviously I was off on that guess. I'm also open to the idea that the sand (play sand) may contain enough fine calcium bits to affect pH on its own. At the same time, I'll be making sure the cold tank doesn't drop much further, I've got a small, nicely shaped piece of white rock here, perhaps I'll pop that in later this week when I do their scaping and see if that levels it all out.